With a view to reducing leak current, enhancing the capacitance (gain) and improving the mobility, a gate insulating film formed by stacking (i) a first layer made of, for example, silicon dioxide (SiO2) having low relative permittivity but allowing for reduction of the interface state density and (ii) a second layer made of a high-k material (oxide or oxynitride of, for example, Hf or Zr) having high relative permittivity is used as the insulating film material for semiconductors. In such technologies, the first layer is stacked on a semiconductor layer, and the second layer is placed between the first layer and a gate electrode layer.